Directional underwater magnetostriction transducer



arch 1, 1963 R. E. BLAND ETAL 3,2,4QE

DIRECTIONAL UNDERWATER MAGNETOS TRICTION TRANSDUCER Filed Nov. 21, 19562 Sheets-Sheet l 85 0| I as a7 F as Hm? INVENTORS BY wad.

KC. W

ATTORNEYS March 19, 1963 R. E. BLAND ETAL 3,

DIRECTIONAL UNDERWATER MAGNETOSTRICTION TRANSDUCER Filed Nov. 21, 1956 2Sheets-Sheet 2 FIG.3

RICHARD E. BLANO JOHN E. LEFRANCOAS WILLIAM J. LEI-9S HARRY E WEGENERINVENTORS IO N ATTORNEYS 3,982,401 Patented Mar. 19, 1963 3,682,461DIRECTEONAL UNDERWATER MAGNETG- STRitITlfiN TRANSDUCER Richard E. Bland,.iohn E. Le Francois, and Wiliiam J. lleiss, State Coliege, and Harry F.Wegener, Bellefonte, 133., assignors, by mesne assignments, to theUnited States of America as represented by the Secretary of the NavyFiled Nov. 21, 1956, Ser. No. 629,430 19 Claims. (Cl. 34ii11) Thisinvention relates to underwater signalling apparatus, and moreparticularly to magnetostrictive type transducers having a planar arrayof individual units so disposed as to produce desired directionaleffects used especially in underwater signalling at substantial depths.In this connection signalling is intended to include both the generationand/or detection of frequencies within as well as above the audiblerange.

Electromechanical transducers for use in water at sonic and ultrasonicfrequencies commonly employ laminated electroresponsive units having agenerally U-shaped form with the active face located at the bight of theU. Excitation and improved directivity of transducers utilizing suchelectroresponsive or maguetostrictive units are commonly secured byproviding series windings having greater or lesser number of turns oneach leg of each unit whereby a desired pattern having certaindirectional characteristics may be secured.

Construction of transducers comprised of generally U- shapedmagnetostrictive units referred to hereinabove having series windings ofopposite polarity on the restricted portions of each unit has heretoforebeen difiicult and time consuming due to the configuration of theU-shaped magnetostrictive units which does not lend itself to thewinding of coils on each leg. Heretofore it has been the practice towind each coil by hand or with special winding apparatus and tointerconnect the coil wires on each unit prior to bonding each unit toan acoustic window. In addition to the time factor involved thisprocedure is particularly disadvantageous in that a high degree of skillis necessary to assemble such a transducer and if a coil is improperlywound, the proper polarity is not observed or an improper connection ismade it is very diflicult if not impossible, to correct such errors. Asmay now be obvious, such transducers are not amenable to repair ormodification and an error in construction or a coil failure generallyresults in the loss of the entire transducer. As may now be alsoobvious, such transducers are not adaptable to mass production methodsand require specially trained and highly skilled personnel for theirconstruction thereby resulting in undue assembly time and constructioncosts. Thus, it is one of the objects of the present invention toprovide a magnctostriction transducer that lends itself to massproduction and that can be more easily and simply constructed.

Another object of the present invention is to provide a magnetostrictiontransducer employing an array of vibrator units having removablewindings whereby such a transducer may be more easily constructed,modified, or repaired.

Another object of the present invention is to provide a winding harnessfor magnetostriction transducers employing an array of vibrator unitsthat may be separately assembled more easily and quickly and that iseasily removable in part or in combination.

Still another object of the present invention is to provide a removablwinding harness for magnetostriction transducers employing an array ofvibrator units that will allow substantially improved and more versatileutilization of multiple windings on each vibrator unit.

It is known in the underwater echo-ranging art that the absorption ofso-called acoustic signals in water is de pendent upon frequency and isinversely proportional to the square of the distance and that for aparticular frequency an underwater transducer has an optimum size formaximum range. It is also well known that the directivity of anunderwater transducer is increased by making the transmitting face largerelative to the wave length in water and that the effect of a large facecan be obtained by using a large number of small vibrator unitspositioned in a common surface. It is further well known thatdirectional characteristics can be improved in some respects and forsome purposes by shading, which is to say, by making the vibrator unitsprogressively less sensitive from the middle to the outer edge, i.e.,directivity and increased range may be secured by shading and byoperating at a lower frequency but in order to maintain the same degreeof directivity the size of the transmitting face must be increased.

Optimization of frequency and transducer size for maximum range is notdiflicult for shipmounted sonar, because the transducer is alwaysrelatively close to the surface and hydrostatic pressure on thetransmitting sur face of the transducer is small. Although submarinesdive to substantial depths, the effects of hydrostatic pressure on thetransmitting surface of submarine mounted sonar are negligible becausethe vibrator units are generally mounted on a spool-like frame. Sincethe hydrostatic pressure is transmitted through the vibrator units tothe core of the spool, and since this force is equal in substantiallyall directions normal to the transmitting surface little or nodeformation or misalignment of the vibrator units occur.

Still further, the selection of a transmitting face area and suitablereinforcement thereof is not limited since submarine borne sonar is to asubstantial degree neither space nor weight limited.

In torpedo echo-ranging systems it has been found preferable to use atransducer comprised of a plurality of vibrator units positioned in asingle plane and to utilize amplitude or phase comparison to determineazimuth and target angle. It has been "found that for a phase comparisonsystem the time required for a signal to first strike one vibrator unitand then the next vibrator unit is critical and hence that it isessential that the front surface of each vibrator unit remain in thesame or a fixed plane at all times. As with ship borne sonar,misalignment of the vibrator units does not occur in a torpedo utilizinga transducer comprised of a planar array of vibrator units when thetorpedo is fired at or near the surface.

However, hydrostatic pressure has heretofore seriously limited theeffectiveness and range of anti-submarine torpedoes in that optimumoperation of a transducer utilizing a planar array is particularlysensitive to hydrostatic pressure for the reason pointed outhereinabove, in addition to the fact that such a transducer is space andweight limited. 7

Heretofore it has been the general practice to utilize either fourseparate generally forward looking transducers each having a relativelysmall transmitting surface or a small single transducer having a planararray, such single transducers having a maximum diameter of about sixinches. With regard to deep running torpedoes, heretofore thehydrostatic pressure present at such depths in combination with otheroperational requirements required the use of a relatively smalltransmitting surface which in turn placed limitations on thetransmitting frequency and directivity. Although such practice permitstorpedo echo ranging or homing at substantial depths, this type ofconstruction and operation required a relatively high transmittingfrequency which seriously limited the range and effectiveness of thetorpedo.

comprises a laminated core of general U-shape.

It is,-thereforc, another object of this invention to provide anunderwater magnetostriction transducer employing a planar array ofvibrator units for use especially at great depths.

It is another object of this invention to provide a substantiallyimproved construction of magnetrostriction transducers employing aplanar array of vibrator units for for-acoustically isolatingthetransducer from the torpedo V shell is utilized in cooperation withother new and novel features to provide improved directional and rangecharacteristics at depths as deep as 1000 feet.

These and other objects and features of the invention, together withtheir incident advantages, will be more readily understood andappreciated from the following detailed description of a preferredembodiment thereof selected for purposes of illustration and shown inthe accompanying drawings, in which:

FIGURE 1 is a cross sectional view with reference to line 1-1 of FIGURE3 of a fully assembled torpedo mountedtransducer incorporating featuresof the present invention.

FIGURE 2 is a cross sectional view taken on line 2-2 of FIGURE 1 toillustrate more clearly the relationship of the vibrator units andassociated parts.

FIGURE 3 is a rear view of a partially assembled transducer toillustrate more clearly constructional features of the presentinvention.

Referring first to FIGURE 1 and FIGURE 2, the transducer thereindisclosed comprises a rigid circular grid 10 having openings 11 tofreely receive a plurality of magnetost'rictive vibrator units 12, and acircular rubber window 13 bonded to the front surface 14 of the grid 10and to the working surface 15 of each magnetostrictive vibrator unit 12.The windings 16 for each vibrator unit arewound on coil forms 17 adaptedto slip over the legs 18 of each vibrator unit and are interconnected inthe desired manner by means 'of a printed circuit 19having providedthereon'th'e necessary terminals 21 and elec-i 'trical circuits '22. Thecoil forms 17 with the windings 16 assembled thereon and connected tothe printed circuit 19, terminal leads 23, and electrical connectors 24(see FIGURE 3) are hereinafter referred to as the winding harness. Arigid circular backup plate 25 is held in fixed spaced relationship withthe grid 10 by means of standoff bolts 26 or the like and acousticallyisolated from the vibrator units 12 by means of a pressure releasematerial '27, such as tor -example, Fairprene, a fabric 'coated with asynthetic elastic composition, or the like.

The outer rear periphery 28 of the grid :is supported by and held in anormally fixed position by, although acoustically isolated from, theforward periphery 29 of the torpedoshell 31'. In a like manner, theouter rear periphery 32 of the backup plate 25 is supported by and heldin a normally fixed position by acoustic isolation means fixed to orcarried by a portion of the torpedo shell rearward of the most forwardperiphery 29 of the torpedo shelll As best shown in FIGURE 2, eachvibrator unit 12 The shape of the vibrator units 12 shown in thedrawings is V in substantial accordance with that shown and described inPatents Numbers 2,550,771,.issued May 1, 1951, and 2,530,224, issuedNovember 14, 1950, to which reference is made. It is to'be understood,however, that the present invention is not limited to utilization ofmagnetostriction cores of the particular shape shown or referred to andmay utilize other various known types of magnetostrictive cores.

As shown in FIGURE 2, the solid end 33 of the vibrator units areutilized to form a working face 15 which is bonded to the inner surface34 of the rubber window 13. As used herein, the working face of eachvibrator unit means the face in direct sound transmitting and receivingrelation to the fluid medium through which the sound is to betransmitted or received. The rubber window 13 is preferably comprised ofRho C rubber or the like which is known to have substantially the sameacoustic impedance as water and to propagate sound waves in the samemanner. It is to be noted that the present invention is not applicableto transducers having heavy metal diaphragms and is applicable only tothe type disclosed herein, in which the front surfaces of the individualvibrator units themselves constitute the working face. The rubber window13 preferably has a substantially flat circular front surface 35 and ithas been found that a thickness of about one inch is satisfactory. foundthat a radius of curvature of the outer'periphery 36 of the rubberwindow of about two inches is satisfactory although the degree ofcurvature is not critical. It is to be noted, however, that somecurature is necessary to prevent an undue amount of cavitation at theperiphery .ity and which are adapted to freely receive the vibratorunits 12 with their respective coil forms 17 and windings 16. In orderto provide maximum rigidity of the grid and minimum extrusion of rubberbetween the. grid openings '11 and their respective vibrator units, itis desirable that the forward portion 37 between each'grid opening 11 beas large as possible,there being a small clearance space 53 at allpoints between the vibrator units 12 and the grid 10. Dueto the more orless T-shape cross section of each vibrator unit in the horizontal planeand its rectangular cross section in the vertical plane as shownrespectively in FIGURE 2 and FIGURE 1, it has been found preferable toundercut the rear portion 32 of the horizontal portions'of the gridbetween each grid opening 11 and also the outer-surface41 of each outergrid opening for the case of vertically disposed coil forms to provideclearance for the coil forms 17 and the windings 16 thereon whilemaintaining minimum clearance between the front portion 37' between gridopenings and the working surface 15 of ecah vibrator'unit.

The thickness of the grid is not critical and may vary within certainlimits depending on structural requirements, the length of the vibratorunits and the number of windings on each vibrator unit. For operation atdepths at least as deep as 1000 feet an aluminum grid having a thicknessof about one inch has been found satisfactory when reinforced in themanner described hereinafter. It is also believed that the undercuttingof grid portions 39 provides in effect a dual layer grid which tends to'damp the grid thus also tending to break up the nodes of vibration ofthe grid and the existance of a resonant frequency for the grid. V i

As best shown in FIGURE 1 and FIGURE 2, the coil tion 42 of eachvibrator unit leg 18; The length of the coil forms 17 may vary and willdepend upon the-size of the vibrator'units that are used, the number ofcoils it is 'desired to wind on each coil form and the method'and meansused to prevent movement orvibration of the coil forms on the legs ofthe vibrator units. g

.It has heretofore been the practice to windeach ,vi-

It has been 7 brator unit winding directly on both legs of each vibratorunit to reduce leakage reactance as much as possible. Further, it hasalso been the practice and considered necessary that one half of eachvibrator unit winding be wound in opposite directions on each leg of thevibrator unit.

It has been found that the provision of windings as and for the purposesdescribed herein, even though the air gap is materially increased, doesnot materially affect the operation of the transducer and that if it isdesired to provide a plurality of windings on each vibrator unit anentire winding may be wound on one portion of a single coil form wherebyat least six separate windings may be easily and simply provided on asingle vibrator unit which has heretofore not been thought feasible.

The windings 16 for each vibrator unit may be wound on the coil forms 17in any conventional manner either all on one coil form or dividedequally between the two coil forms for each vibrator unit. A compressivematerial 43 such as rubber or the like may be afiixed to the outer lowerportion 44 of each vibrator unit to acoustically isolate the lowerportion of each coil from the vibrator unit and a compressible material45 substantially cylindrical in form such as for example rubber hose,may be inserted above the coil forms to hold the upper end of the coilforms in place and also support the end portion of magnets 46. Magnets46 are held in place by friction between legs 13 of vibrator units 12and retained 'by a fibrous adhesive tape in a manner well known in theart. The compressible material 43 and 45 in contact respectively withthe lower and upper portions of each coil form- 17 allows any necessarymovement of the coil forms but holds the coil forms in a substantiallyfixed position thereby resulting in substantially reproducible vibratorunit electrical characteristics and also provides a substantial measureof acoustic isolation thereby preventing the generation of noise and thelike in the transducer as a result of vibrations of the coil forms 17due to external sources.

Interconnection of the vibrator unit windings is provided by a printedcircuit 19 wherein the desired circuitry 22 and assembly information isprinted in any conventional manner on a suitable dielectric base 47 suchas ethoxyline glass fabric or the like. In addition to the printedelectric circuitry 22 and terminal pins 21, the base 47 is provided withholes 49 to receive the mounting means for the backup plate (in thiscase 9 standoff bolts) and holes 51 (in this case 52) formed andpositioned in accordance wtih the grid holes and adapted to freelyreceive the vibrator units 12 and their assembled coil forms 17.

After the windings 16 for each individual vibrator unit have been woundon the coil forms 17, the coil forms may be placed in the holes 51 inthe printed circuit base 47 corresponding to their respective vibratorunit and the leads 52 from each winding may then be easily and quicklysoldered to its respective terminal 21 on the base 47. The pattern arrayterminals 53 for each pattern array may be placed on the periphery ofthe base 47 and Wires 23 soldered to these terminals to form a cable forconnection to an electrical connector 24-. As shown in FIGURE 3,electrical circuitry and connections for three separate pattern arraysare shown, but it is to be tinderstood that a greater or lesser numberof pattern arrays comprised of a greater or lesser number of individualwindings may be used and the output and/ or input wires for each patternarray may be combined and terminate in one or more electric connectorsAs mentioned herein above, the connector wires 23 of each pattern arraymay be combined into a single cable and electric connector but it hasbeen found preferable and desirable that the connector wires for certainarrays be separated and disposed away from the connector Wires ofcertain other arrays to reduce crosstalk and simplify construction andrepair or testing.

removed and/or replaced When assembled the winding harness comprisingthe coil forms, printed circuit, connector wires and electric connectorsmay be mounted on the vibrator unit assembly by sliding the coil forms17 down over their respective legs 18 of the vibrator units 12andaflixing the printed circuit 19 to the inner surface 54 of the gridby means of screws 55 or the like.

It is the general practice in the design of underwater phase comparisontransducers to space the vibrator units less than one wavelength apart,the usual spacing being of the order of one-half wavelength. Although itshould be understood that the features of construction of the presentinvention are applicable to high resonant frequency transducers as Wellas those having a low resonant frequency, a point may be reached at thehigher frequencies where there is insufficient space between thevibrator units for all the desired connections to be made on one printedcircuit, or alternately, it may be desired to employ such a number ofwindings on each vibrator unit, such as for example, six windings, thatthe interconnections for such windings cannot be printed on one base.These disadvantages may be simply and easily overcome by using two ormore printed circuits and stacking them in fixed spaced relationship oneabove the other. For example, the windings on the right leg of thevibrator units may be connected to one printed circuit and the windingson the left leg connected to a second printed circuit or all thewindings of a portion of the vibrator units may be connected to a firstprinted circuit, all the windings of another portion of the vibratorunits may be connected to a second printed circuit, another portion toanother printed circuit, etc., and if necessary, the various printedcircuits can then be interconnected as desired by wires or the like.

It may now be obvious that utilization of coil forms and a printedcircuit in the manner'described herein greatly simplifies constructionand the interconnection of the vibrator unit windings 16 and provides aunitary removable winding harness that may be simply and quicklyassembled or removed. Further, a single coil form or a plurality of coilforms may also be easily and quickly or repaired as is not possible orfeasible in prior art transducers. Still further, utilization of aprinted circuit allows the printing of assembly information anddirections which greatly facilitate construction and repair with aproportionate reduction in possible assembly errors since the positionof the magnet in each vibrator unit and the direction of Winding thecoils for each vibrator unit must have a fixed pre-determined relation.

For operation at depths as deep as 1000 feet where the hydrostaticpressure is of the order of 500 pounds per square inch, it may beobvious that the relatively thin grid will not withstand such forces oreven maintain the working faces 15 of the vibrator units in a commonplane. As mentioned previously herein, it is essential in a transducercomprising a part of a phase comparison detection system that theworkingfaces of the vibrator units remain at all times substantially in thesame plane. Experience has shown that'a misalignment of the working faceof vibrator units of about of an inch or more 'with the Working surfaceof other vibrator units materially reduce the effectiveness and ducer.

In order to help overcome the above mentioned undesirable condition,there is provided in combination with the grid 16 a relatively thickbackup plate 25 comprised of aluminum, steel, or the like held in fixedspaced relationship with the rear surface 34 of the grid by standoffbolts 26 or the like.

As shown in FIGURE 1 and FIGURE 3, nine standoff bolts or spacers 26 areutilized to hold the backup plate 25 in fixed spaced relationship withthe rear surface 34 of the grid, four being located for abuttingrelationship with the periphery of the backup plate and spaced accuracyof the transbolts 26.

degrees apart and five being located in the center portion 56 of thegrid for abutting relationship with the center portion of the backupplate.

The number, position and length of the standoff bolts or spacers are notbelieved critical so long as at maximum operating depth, the grid iskept substantially coplanar with the backup plate within the limitsspecified hereinabove'. The standoff bolts 26 which are positioned forand in abutting relationship with the outer periphery of the backupplate, have a threaded forward portion adapted for threaded engagementwith the grid, a cylin drical middle portion and an internally threadedrear portion adapted to receive the .backup plate bolts 57. Thecentrally located standoff bolts 26 are similar to the peripherallylocated standoff bolts except that their rear portions are notinternally threaded. The front surface and rear surface of the standoffbolts should preferably be coplanar with respectively the grid and thebackup plate.

A pressure release material 27 such as for example 'Fairprene, afabriecoated with a synthetic elastic composition, or the like, havingholes 58 provided to receive the rear portion of the standoff bolts, isdisposed between the rear surface of the vibrator units and the frontsurface of the backupplate to acoustically isolate and insulate thevibrator units from the backup plate and to prevent u crosstalk betweenvibrator. units. The backup plate is additionally provided with fourcounter bored holes 59 in axial alignment with the peripherally locatedstandoff bolts 26 to freely receive the backup plate bolts 57 which areadapted for threaded engagementwith the internally threaded rear portionof the aforementioned standoff As 'mentioned previously hereinabove, thelength of the standoff bolts 26 is not critical in terms of over-alllength, but it is important that the standoff bolt be so formed and ofsuch a length and that the front surface 61 of the backup plate is heldsubstantially coplanar with the front surface of the grid such that whenthe backup plate bolts '57 are tightened, the pressure release material27 interposed between the vibrator units and the backup plate will exerta small amount of pressure on the rear surfaces of the vibrator unitswithout disturbing the aforementioned coplanar relationship of thevibrator unit working surfaces 15. It has been found that if the frontand 'rear surfaces of the grid are coplanar with the front surface ofthe backup plate andthe length of the standoff 'bolts are held to atolerance of :IDOZ inch, the vibrator unitswill be properly positioned.

As best shown in FIGURE 2, the backup plate is additionally providedwith at least one,(in the present invention there are 3) counterboredtransverse passages 62 adapted to receive the output leads 23 andelectrical connectors 24 of the pattern arrays. To facilitate assemblyand dis-assembly of the transducer, it is desirable that the connectorwires 23 of the pattern arrays be fixedly connected as by soldering toelectrical connectors 24 that are separable from the backup plate 25such that the backup I less than the diameter of the backup plate.

plate may be removed and separated from the winding harness withoutdisturbing the soldered connections of the electrical connectors 24. I

separability of the backup plate and the electrical connectors may beachieved by using conventional connectors such as for example AN 3 102connectors. By providing' I sufficiently long connector wires 23, afterassembly the center portions 63- of each electrical connector 24 may bepassedrforwardly through the passages 62 by first removing screws 64,pulling the connector 24 rearwardly sufficient to allow removal of theretaining ring 65 and then passing the center portion 63 forwardlythrough passage 62. For assembly the above procedure is simply reversed.

In addition to the grid and backup platethere is pro-'videdacousticisolation and reinforcing means in which the forwardportion of the torpedo shell 31 forms an in- 'present invention andwhich cooperate with the grid and backup plate to insure maintenance ofproper vibrator unit location at substantial depths. The forward portionof the acoustic isolation and reinforcing means is comprised of aninwardly protruding pressure ring 66 having a front surface 67substantially transverse to the longitudinal axis of the torpedo andattached to the extreme forward periphery 29 of the torpedo shell as bywelding or the like and having a plurality of transverse holes 68 on acommon bolt diameter to freely receive the mounting bolts 69 and theacoustic isolation bolts 71. A plurality of layers of acoustic isolationmaterial 72 such as for example, Fairprene, a fabric coated with asynthetic elastic composition, or the like, having poor soundtransmitting properties and of the same general configuration as thepressure ring 66 are provided between the pressure ring 66 and amounting ring 73 which are all held in watertight relation by theacoustic isolation bolts 71 which are acoustically isolated from thetorpedo shell by isolation washers 74. The mounting ring 73 is adaptedfor threaded engagement with the acoustic isolation bolts 71 and hasprovided in its front surface an annular groove 75 adapted to receive anO-ring 76 to provide a watertight seal between the mounting ring '73 andthe grid 10.

The mounting ring 73 and the acoustic isolation material 72 are furtherprovided respectively with a plurality of transverse holes and 89 (inthis case 6) to freely receive the mounting bolts 69 which are adaptedfor threaded engagement with the outer periphery of the grid as atpoints 91 and which provide the sole means for securing the vibratorunit assembly to the acoustic isolation and reinforcing means morethoroughly described and discussed hereinbelow.

Radially spaced ribs 77 parallel to the longitudinal axis of the torpedoin abutting relation with the rear surface 78 of the pressure ring 66and affixed to the torpedo shell 31 as by welding and the like providereinforcement of the pressure ring 66. Although a welded constructionhas been described it is to be noted that the pressure ring 66 and thereinforcing means thereof such as for example, radial ribs 77 or thelike, may be formed as an integral part of the torpedo shell.

As will be more fully explained later, it is considered important thatthe mounting ring 73 be acoustically isolated from the torpedo shell 31and it is considered essential that it be attached thereto in such amanner that as pressure is applied to the frontsurface of the rubberwindow 13, the grid may move rearwardly as a unit a certain distancedepending upon the compressibility of the acoustic isolation material72.

The rear portion of the aforementioned acoustic isolation andreinforcing means is comprised of a second annular ring-like pressurering 79 carried by a plurality of gussets or longitudinal ribs 81 andhas an inside diameter The gussets or longitudinal ribs 81 may beattached to the inner surface of the torpedo shell "31 as by welding orthe like or,

alternately, may be formed as an integral part of the torpedo shell asmay the second pressure ring 79.

The seeond'pr'essure ring 79 is provided with a plurality of transverseholes 82 on a common bolt diameter adapted'to freely receive alike'number of acoustic isolation bolts 83, the rear portions of whichare acoustically isolated from the pressure ring as by isolation washers84. An annular ringlike spacer ring adapted for threaded engagement withthe isolation bolts 83 and a plurality of x 7 9 83. For convenience inmounting and removing the vibrator unit assembly access holes 92 may beprovided in the second pressure ring 79 in axial alignment with andhaving the same diameter as holes 89 in the forward pressure ring 66.

It is believed essential for optimum operation of the transducer atsubstantial depths that the front surface 33 of the spacer ring 85 andthe peripheral rear surface 32 of the backup plate in contact with thespacer ring be in a plane substantially transverse to the longitudinalaxis of the torpedo, or, to say it another way, substantially coplanarwith the grid surfaces, and that they be a predetermined distancerearwardly of the front surface of the mounting ring, such distancebeing such that when the vibrator unit assembly is mounted in thetorpedo proportional forces will be exerted on the forward and rearwardacoustic isolation material 72 and 86. It has been found preferable thatthis distance be within a tolerance of i.002 inch.

This distance and the coplanar relationship of the various surfaces asindicated hereinabove may be held within the desired tolerance if priorto mounting the vibrator unit assembly in the torpedo the forwardisolation bolts 71 and the rearward isolation bolts 83 are tightenedwith substantially the same amount of tension, thereby subjecting theforward acoustic isolation material 72 and the rearward acousticisolation material 86 to the same amount of compressive force, and thensecuring the proper distance between the front surface of the mountingring and the front surface of the spacer ring by forming these surfaceson a lathe after assembly in the torpedo.

As may now be apparent, the present invention as disclosed and describedherein incorporates, for a torpedo installation, the forward portion ofthe torpedo as an integral part of the transducer to provide an improvedtransducer having a larger diameter and occupying a minimum amount ofspace and having improved range and directional characteristics for useespecially at substantial depths. Additionally, the acoustic isolationmeans for the vibrator unit assembly is utilized in cooperation with thetorpedo shell reinforcing means in a new and novel manner to insure theproper alignment of the vibrator units at substantial depths.

It may now also be obvious that to insure the proper alignment of thevibrator units it is necessary that as the hydrostatic pressure on theface of the transducer in creases, the outer periphery of the grid andthe outer periphery of the backup plate remain in a fixed relation onewith the other as well as their center portions. An acousticallyisolated but unyielding connection at one peripheral point but not atthe other results, at substantial depths, in distortion of the vibratorunit assembly and hence, misalignment of the vibrator units. Anunyielding connection at both points, while satisfactory from astructural point of view, is unsatisfactory because of the high soundtransmitting propert es of such a connection thereby resulting indetection by the vibrator units of torpedo machinery noise and the likeand hence, an undesirably high background level.

The optimum in acoustic isolation and structural requirements issubstantially attained by the construction shown and described hereinwhere in addition to an integrated grid and backup plate, thiscombination is acoustically isolated at the structural reinforcementpoints and wherein the acoustic isolation is so constructed and designedas to be compressible in the direction of the compressing force wherebythe entire vibrator unit assembl is allowed to move rearwardly, albeit avery small distance, the compressive force thereby being substantiallyequally distributed at the pohits of reinforcement from maximumhydrostatic pressure to minimum hydrostatic pressure thereby alsoallowing an accurate determination of and a proportionate reduction inthe structural strength of the points of reinforcement.

It may now be seen that there has been shown and described a transducerconstruction having improved range and directivity characteristics foruse especially at substantial depths in combination with a torpedo. Itis to be noted and understood, however, that the construction andcomponents as shown and described herein are subject to modification asis the use and installation of the transducer since it may be used withunderwater bodies other than a torpedo and in underwater installationswithout departing from the spirit and scope of the invention.

The construction shown and described herein is in many respectsinexpensive to fabricate and is versatile as to construction,modification, repair, and use. It also lends itself readily to massproduction methods thereby resulting in less expensive transducers andtransducers having more predictable and more uniform characteristics.Still further, it allows the use in a torpedo of an improved directionaltransducer having a working face that approaches the diameter of thetorpedo, that occupies a minimum amount of space, and that has improveddirectional characteristics at maximum operating depth substantially thesame as its directional characteristics at minimum operating depth.

While the present invention has been described in its preferredembodiment, it is realized that modifications may be made, and it isdesired that it be understood that no limitations upon the invention areintended other than may be imposed by the scope of the appended claims.

Having now disclosed our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

1. An underwater transducer comprising: an outer shell open at one end;a vibrator unit assembly, said vibrator unit assembly comprising arearwardly movable first rigid plate, said plate having a plurality ofopenings in predetermined different positions, an acoustic window bondedto said first plate, said acoustic window having a front surface exposedto the water and a fiat rear surface, an array of individualmagnetostrictive vibrator units having individual rear surfaces andhaving individual working faces of substantial area affix-ed to saidacoustic window, one each being positioned in each of said openings,windings associated with said vibrator units, a rearwardly movablesecond rigid plate held in fixed spaced relationship with said firstplate, and acoustic isolation means interposed between said 'vibratorunit rear surfaces and said second plate; and reinforcing means carriedby said shell and in abutting relationship with said first and secondplate whereby said first and second plates are maintained insubstantially coplanar relationship as hydrostatic pressure on the frontsurface of said acoustic window increases.

2. An underwater transducer comprisingt an outer shell open at one end;a vibrator unit assembly, said vibrator unit assembly comprising arearwardly movable first rigid plate, said plate having a plurality ofopenings in predetermined different positions, an acoustic window bondedto said first plate, said acoustic window having a front surface exposedto the water and a flat rear surface, an array of individualmagnetostrictive vibrator units having individual rear surfaces andhaving individual working faces of substantial a-rea affixed to saidacoustic window, one each being positioned in each of said openings,windings associated with said vibrator units, a rearwardly movablesecond rigid plate held in fixed spaced relationship with said firstplate, and acoustic isolation means interposed between said vibratorunit rear surfaces and said second plate; and means to reinforce saidvibrator unit assembly carried by said shell in peripherially abuttingrelationship with 'said first and second plate whereby said first andsecond plates are maintained in mutual coplanar relationship ashydrostatic pressure on the front surface of said acoustic windowincreases.

3. An underwater transducer comprising: an outer shell open at one end;a vibrator unit assembly, said vibrator unit assembly comprising arearwardly movable first rigid plate, said plate having a plurality ofopenings in predetermined different positions, an acoustic window bondedto said first plate, said acoustic window having a front surface exposedto the water and a flat rear surface, an array of individualmagnetostrictive vibrator units having individual rear surfaces andhaving individual working faces of substantial area affixed to saidacoustic window, one each being positioned in each of said openings,windings associated with said vibrator units, a rearwardly movablesecond rigid plate in fixed spaced relationship with said first plate,and acoustic isolation means interposed between said vibrator unit rearsurfaces and said second plate; and means to reinforce said vibratorunit assembly disposed between said shell and said first and secondplate whereby said vibrator-unit assembly may move rearwardly ashydrostatic pressure on the front surface of said acoustic windowincreases.

4. An underwater transducer comprising: an outer shell open at one end;a vibrator unit assembly disposed within said shell and closing saidopen end, said vibrator unit assembly comprising a rearwardly movablefirst rigid plate, said plate having a plurality of openings inpredetermined different positions, said openings having a front portionand a rear portion, said front portion having an area less than saidrear portion, an acoustic window bonded to said first plate, saidacoustic window having a front surface exposed to the water and a fiatrear surface, an array of individual longitudinal magnetostrictivevibrator units having individual rear surfaces and having individualworkng faces of substantial area affixed to the rear surface of saidacoustic window, each of said working faces having an area less than thearea of the front portion of each if said openings, one vibrator beingcentered in each of said openings, windings associated with saidvibrator units, a rearwardly movable second rigid plate held in fixedspaced relationship with said first plate, and acoustic isolation meansinterposed between said vibrator unit rear surfaces and said secondplate; and reinforcing means carried by said shell and in abuttingrelationship with said first and second plate whereby said first andsecond plates are maintained in substantially coplanar relationship ashydrostatic pressure on the front surface of said acoustic windowincreases. 7

5. A transducer according to claim 4 in which'the thickness of the firstplate is substantially less than the length of said vibrator units.

' 6. An underwater transducer comprising: an outer shell open at oneend; a vibrator unit assembly disposed within said shell and closingsaid open end, said vibrator unit assembly comprising a rearwardlymovable first rigid plate, said plate having a plurality of openings inpredetermined different positions, said openings having a front portionand a rear portion, said front portion having an area less than saidrear portion, an acoustic window bonded to said first plate, saidacoustic window having a front surface exposed to the water and a flatrear surface, an array of individual longitudinal megntostrictivevibrator units having individual rear surfaces and having individualworking faces of substantial area affixed to the rear surface of saidacoustic window, each of said working faces having an area less than thearea of the front portion of each of said openings, one vibrator beingcentered in each of said openings, windings associated with saidvibrator units, a rearwardly movable second rigid plate in fixed spacedrelationship with said first plate, plate, spacing means interposedbetween and connecting said' first and said second plate whereby saidfirst and said second plate may be held in substantially coplanarrelationship, and acoustic isolation means interposed be:

tween said vibrator unit rear surfaces and said second plate; and meansto reinforce said vibrator unit assembly disposed between said shell andsaid first and second plate whereby said vibrator unit assembly may moverearwardly as hydrostatic pressure on the front surface of said acousticwindow increases.

7. A transducer according to claim 6 in which the spacing meanscomprises a plurality of longitudinal elements disposed at the peripheryand center of said first and second plates.

8. An underwater transducer comprising: an outer shell open at one end;a vibrator unit assembly, said vibrator unit assembly comprising a firstrigid plate, said plate having a plurality of openings in predetermineddifferent positions, an acoustic window bonded to said first plate, saidacoustic window having a front surface exposed to the water and a fiatrear surface, an array of individual longitudinal magnetostrictivevibrator units having individual rear surfaces and having individualworking faces of substantial area affixed to said acoustic window, onevibrator being positioned in each of said openings, windings associatedwith said vibrator units, a printed circuit having a plurality ofindividual openings adapted to freely receive said vibrator units, saidprinted circuit providing electrical circuitry for interconnecting atleast a part of the windings, a plurality of coil forms removablycarried by said vibrator units, said windings beingwound on andsupported by said coil forms and connected to said printed circuit in apredetermined manner, a second rigid plate held in fixed spacedrelationship with said first plate, and acoustic isolation meansinterposed between said vibrator unit rear surfaces and said secondplate; and reinforcing means carried by said shell in abuttingrelationship with said first and second plate whereby said first andsecond plates are maintained in substantially coplanar relationship ashydrostatic pressure on the front surface of said acoustic windowincreases.

9. A transducer according toclaim 8 in which the openings in said firstplate have a front portion and a rear portion, said rear portion havingan area greater than said front portion and adapted to freely receivesaid coil forms; and said printed circuit is carried by said'firstplate.

10. An underwater transducer comprising: an outer shell open atone end;a vibrator unit assembly, said plate, said acoustic window having afront surface exposed to the Water and a flat rearsurface, an array ofindividual U-shaped magnetostrictive vibrator units, one each beingcentered in each of said openings, each of said vibrator units beingcomprised of a front portion and two rearwardly extending leg portions,said front portion having a working face of substantial area afiixed tosaid acoustic window and said leg portions having individual rearsurfaces, coil'forms removably carriedby said leg portions, windingscarried by said coil forms, a printed circuit having a plurality ofindividual openings positioned and adapted to freely receive saidvibrator units and said coil forms, said printed circuit providing fixedelectrical circuitry for interconnecting said windings, a second rigidplate held in fixed spaced relationship with said first plate, andacoustic isolation means interposed between said vibrator unit rearsurfaces and said second plate; and reinforcing means carried bysaidshell in abutting relationship with said first and. second platefirst plate.

12. A transducer according to claim 10 in which a plurality' of printedcircuits are provided in stacked spaced relationship and a portion ofsaid windings al'e interconnected by each printed circuit.

13. A transducer comprising: an array of individual U-shapedmagnetostrictive vibrator units, each vibrator unit comprising a frontortion of substantial area and two individual rearwardly extending legportions, each said front portion having a working face positioned in acommon plane; a magnet disposed between the leg portions of eachvibrator unit; a coil from removably carried by at least one leg of eachvibrator unit; a winding carried by each coil form; means removablydisposed between said magnets and said coil form to sup-port saidmagnets and hold said coil forms in a normally fixed position withregard to its respective leg portion; and a printed circuit having aplurality of individual openings positioned and adapted to freelyreceive said vibrator units and said coil forms, said printed circuitproviding electrical circuitry forinterconnecting said windings in apredetermined manner.

14. An underwater transducer comprising: an outer shell open at one end;a vibrator unit assembly disposed within said shell and closing saidopen end, said vibrator unit assembly comprising a rearwardly movablefirst rigid plate, said plate having a plurality of openings inpredetermined different positions, said openings having a front portionand a rear portion, said front portion having an area less than saidrear portion, an acoustic Window bonded to said first plate, saidacoustic window having a ront surface exposed to the water and a flatrear surface,

an array of individual longitudinal magnetostrictive vibrator unitshaving individual rear surfaces and having individual working faces ofsubstantial area aflixed to the rear surface of said acoustic window,each of aid working faces having an area less than the area of the frontportion of said openings, one vibrator being centered in each of saidopenings, windings associated with said vi brator units, a rearwardlymovable second rigid plate held in fixed spaced relationship with saidfirst plate, and acoustic isolation means interposed between saidvibrator unit rear surfaces and said second plate; and means carried bysaid outer shell in abutting relationship with said first and secondplates whereby the outer periphery of said first and second plates areperipherally reinforced and isolated from the shell, said means allowingsaid first and second plates to move rearwardly a substantially equaldistance as the hydrostatic pressure on the front surface of saidacoustic window increases.

15. An underwater transducer comprising: an outer shell open at one endand having a front portion and a rear portion; a vibrator unit assmeblydisposed within said shell and closing said open end, said vibrator unitassembly comprising a first rigid plate, said plate having a pluralityof openings in predetermined different positions, an acoustic windowbonded to said first plate, an array of individual longitudinalmagnetostrictive vibra tor units having individual rear surfaces andhaving individual working faces afiixed to the rear surface of saidacoustic window, one vibrator being centered in each of said openings,windings associated with said vibrator units, a second rigid plate heldin fixed spaced relationship with said first plate, and acousticisolation means interposed between said vibrator unit rear surfaces andsaid second plate; first isolating means disposed in watertightrelationship between the outer periphery of said first plate and saidshell front portion whereby said first plate is acoustically isolatedfrom said shell and may move rearwardly; and second isolating meanscarried by said shell rear portion in abutting relationship with saidsecond plate whereby said second plate is acoustically isolated fromsaid shell and may move in a rearwardly direction substantially the samedistance said first plate moves rearwardly upon application of presusreon the front surface of said acoustic window, said first and secondisolating means additionally providing reinforcement at the outerperiphery of said first and second plates.

16. A transducer according to claim 15 in which said first isolatingmeans comprises an inwardly extending first pressure member adapted :toperipherially reinforce said first plate and longitudinally compressibleacoustic isolation material disposed between said first pressure memberand said first plate; and said second isolating means comprises aninwardly extending second pressure member adapted to peripheriallyreinforce said second plate and longitudinally compressible acousticisolation material disposed between said second pressure member and saidsecond plate whereby the pressure on said isolation material in saidfirst and second isolating means remains substantially equal.

17. In a directional transducer for use in torpedoes and adapted for useespecially at substantial depths the combination comprising: an outershell substantially open at one end and forming the most forward portionof the torpedo body; a rearwardly movable first rigid plate transverseto said open end, said first plate having a plurality of openings inpredetermined different positions, an acoustic window bonded to saidfirst plate and substantially closing said open end, said acousticwindow having a front surface exposed to the water and a flat rearsurface; an array of individual magnetostrictive vibrator units havingindividual rear surfaces and having individual working faces ofsubstantial area afiixed to said acoustic window rear surface, onevibrator being positioned in each of said openings; windings associatedwith said vibrator units; a rearwardly movable second rigid plate heldin fixed spaced relationship with said first plate; acoustic isolationmeans interposed between said vibrator unit rear surfaces and saidsecond plate; and reinforcing means carried by said shell in abuttingrelationship with said first and second plate whereby said first andsecond plates are maintainde in substantially coplanar relationship ashydrostatic pressure on the front surface of said acoustic windowincreases.

18. In a directional transducer for use in torpedoes and adapted for useespecially at substantial depths the combination comprising: an outershell substantially open at one end and forming the most forward portionof the torpedo body; a rearwardly movable first rigid plate transverseto said open end, said first plate having a plurality of openings inpredetermined different positions, an acoustic window bonded to saidfirst plate and substantially closing said open end, said acousticwindow having a front surface exposed to the water and a flat rearsurface; an array of individual magnetostrictive vibrator units havingindividual rear surfaces and having individual working faces ofsubstantial area affixed to said acoustic window rear surface, onevibrator being positioned in each of said openings; windings associatedwith said vibrator units; a rearwardly movable second rigid plate heldin fixed spaced relationship with said first plate; acoustic isolationmeans interposed between said vibrator unit rear surfaces and saidsecond plate; and means to reinforce and isolate said first and secondplates disposed between said shell and said first and second platewhereby said first and second plates may move rearward-1y asubstantially equal distance as hydrostatic pressure on the frontsurface of said acoustic window increases.

19. In a directional transducer for use in torpedoes and adapted for useespecially at substantial depths the combination comprising: an outershell substantially open at one end and forming the most forward portionof the torpedo body; a first rigid plate transverse to said open endhaving a front surface and a rear surface, said first plate having aplurality of openings in predetermined different positions, saidopenings having a front portion and a rear portion, said front portionhaving an area less than said rear portion, an acoustic window bonded tothe front surface of said first plate and substantially closing saidopen end, said acoustic window having a front surface exposed to thewater and a flat rear surface; an array of individual magnetostrictivevibrator units having individual rear surfaces and having individualworking faces of substantial area aflixed to said acoustic window rearsurface, each of said Working faces having an area, slightly less thanthe area of the front portion of each of said openings, one vibratorbeing centered in each of said openings; windings associated with saidvibrator units; a second rigid plate disposed a fixed distancerearwardly of said first plate and substantially parallel therewith;spacing means interposed between said first and second plates wherebysaid first plate may be held in substantially fixed coplanarrelationship with said second plate; acoustic isolation means interposedbetween said vibrator unit rear surfaces and said second plate; andmeans to reinforce and isolate said first and second plates disposedbetween said shell and said first and second plates whereby said firstand second plates may move rearwardly a substantially equal distance ashydrostatic pressureon the front surface of said acoustic windowincreases.

References Cited in the file of this patent UNITED STATES PATENTS HarrisJuly 28, 1 959

1. AN UNDERWATER TRANSDUCER COMPRISING: AN OUTER SHELL OPEN AT ONE END;A VIBRATOR UNIT ASSEMBLY, SAID VIBRATOR UNIT ASSEMBLY COMPRISING AREARWARDLY MOVABLE FIRST RIGID PLATE, SAID PLATE HAVING A PLURALITY OFOPENINGS IN PREDETERMINED DIFFERENT POSITIONS, AN ACOUSTIC WINDOW BONDEDTO SAID FIRST PLATE, SAID ACOUSTIC WINDOW HAVING A FRONT SURFACE EXPOSEDTO THE WATER AND A FLAT REAR SURFACE, AN ARRAY OF INDIVIDUALMAGNETOSTRICTIVE VIBRATOR UNITS HAVING INDIVIDUAL REAR SURFACES ANDHAVING INDIVIDUAL WORKING FACES OF SUBSTANTIAL AREA AFFIXED TO SAIDACOUSTIC WINDOW, ONE EACH BEING POSITIONED IN EACH OF SAID OPENINGS,WINDINGS ASSOCIATED WITH SAID VIBRATOR UNITS, A REARWARDLY MOVABLESECOND RIGID PLATE HELD IN FIXED SPACED RELATIONSHIP WITH SAID FIRSTPLATE, AND ACOUSTIC ISOLATION MEANS INTERPOSED BETWEEN SAID VIBRATORUNIT REAR SURFACES AND SAID SECOND PLATE; AND REINFORCING MEANS CARRIEDBY SAID SHELL AND IN ABUTTING RELATIONSHIP WITH SAID FIRST AND SECONDPLATE WHEREBY SAID FIRST AND